Surgical site infection in community hospitals

AORN Journal, April, 2008 by George Allen

Annals of Surgery

February 2008

Surgical site infections (SSIs) result in adverse patient outcomes, including increased risk of mortality, longer hospitalizations, and increased cost. Beginning in 2008, institutions will no longer be reimbursed by the Centers for Medicare & Medicaid Services for the additional care provided as a result of an SSI. Furthermore, an increasing number of states have passed laws requiring hospitals to measure and publicly report rates of health care-acquired infections, including SSIs.

The utility of public reporting of SSI rates and the optimal methods to employ when reporting SSI rates remain controversial. Consequently, it is recommended that risk-adjustment techniques be used, such as the SSI risk index used by the National Healthcare Safety Network (ie, formerly the National Nosocomial Infection Surveillance System [NNIS]) that incorporates prospectively applied markers for the likelihood of SSI using patient-specific and perioperative measures of risk. In addition to procedure and patient-specific risk stratification, it is believed that certain hospital-level characteristics, such as volume, may be important determinants of patient SSI risk. The relationship between surgical volume and risk of SSI has not been thoroughly investigated, however. There have been conflicting results, and published reports have not included significant numbers of small and medium-sized community hospitals. The objective of this prospective study was to determine whether surgical volume affects the risk of SSI in community-based hospitals. The a priori hypothesis was that hospital surgical volume would be inversely proportional to the risk of SSI in community hospitals.

The Duke Infection Control Outreach Network (DICON) is a network of 35 community hospitals, with affiliated hospitals located in Virginia, North Carolina, South Carolina, and Georgia. The DICON provides a network approach to infection control, allowing community hospitals to have sophisticated data analysis and metrics, benchmarked data, and access to experts in infection control. From January 1, 2004, to December 31, 2005, prospective data was taken from 18 hospitals in the DICON, and the risk of SSI for each category was determined. Hospitals were separated based on average surgical volume per year:

* small (< 1,500 procedures);

* medium ([less than or equal to] 1,500 to < 4,000 procedures); and

* large ([greater than or equal to] 4,000 procedures).

To help quantify the inherent risk of SSI associated with specific procedures, a binary variable "high-risk procedure" was created. A "high-risk procedure" was defined as a procedure for which the mean rate of SSI published by the NNIS was > 3% for patients with a risk index of 1. Variables with SSI rates [less than or equal to] 3% were classified as low risk. Surgeon experience was calculated by determining the average number of procedures performed annually by each surgeon at each hospital during the study period. Additionally, proximity to a referral center was defined as the distance in miles to the nearest tertiary care center. The risk of SSI for each category was determined using multivariate Poisson regression techniques.

FINDINGS. Prospective surveillance was performed on 132,111 surgical procedures at the 18 hospitals during the two-year study period. A total of 1,434 SSIs were identified (prevalence rate of SSI = 1.09/100 procedures). In unadjusted analysis, the risk of SSI was almost twice as high at small hospitals (prevalence rate ratio [PRR] = 1.9: 95% confidence interval [CI] 1.78-2.05) and large hospitals (PRR = 1.79: 95% CI 1.70-1.90) compared with medium hospitals. After adjusting for differences between hospital category and important confounders, the risk of SSI at small hospitals was still 1.5 times higher than at medium hospitals (adjusted PRR = 1.49: 95% CI 1.39-1.60), whereas the risk at large hospitals was substantially decreased compared with medium hospitals (adjusted PRR = 1.29: 95% CI 1.22-1.36).

CLINICAL IMPLICATIONS. The results of this study revealed that the risk of SSI at small hospitals was higher than at medium and large hospitals. The study authors concluded that hospital surgical volume has an important, complex relationship with rates of SSI in community hospitals and that given the growing momentum for public reporting of SSI rates, epidemiologists and surgeons must continue to analyze surgical volume and other operative variables to improve methods for risk-adjusting infection rates. Perioperative nurses and managers should be prepared to assist in these studies and analyses.

Anderson DJ, Hartwig MG, Pappas T, et al. Surgical volume and the risk of surgical site infection in community hospitals: size matters. Ann Surg. 2008; 247(2):343-349.

GEORGE ALLEN

PHD, RN, CNOR, CIC

DIRECTOR OF INFECTION CONTROL

DOWNSTATE MEDICAL CENTER

BROOKLYN, NY